1) Open Library in a half-screen panel.
2) Click Prioritize.
3) Make the panel somewhat narrower.
4) Click Browse.
>> No circled 'i' to open the Info panel with.
Happens in other circumstances as well, but this was a reproducible case.
Here's a screenshot from a session when there was no 'i' to close the panel with:

As you can see there's not exactly a shortage of space for it.
The 'i' returns if the panel is widened slightly.